Initiates the shutdown sequence of the Java Virtual Machine. Unless the security manager denies exiting, this method initiates the shutdown sequence (if it is not already initiated) and then blocks indefinitely. This method neither returns nor throws an exception; that is, it does not complete either normally or abruptly.

The argument serves as a status code. By convention, a nonzero status code indicates abnormal termination.

Successful invocations of this method are serialized such that only one invocation initiates the shutdown sequence and terminates the VM with the given status code. All other invocations will perform no action and block indefinitely.

Because a successful invocation of this method blocks indefinitely, if it is invoked from a shutdown hook, it will prevent that shutdown hook from terminating. Consequently, this will prevent the shutdown sequence from finishing.

The System.exit method is the conventional and convenient means of invoking this method.

Registers a new virtual-machine shutdown hook.

A shutdown hook is simply an initialized but unstarted thread. Shutdown hooks are started at the beginning of the shutdown sequence . Registration and de-registration of shutdown hooks is disallowed once the shutdown sequence has begun.

Uncaught exceptions are handled in shutdown hooks just as in any other thread, as specified in Thread.UncaughtExceptionHandler. After the uncaught exception handler has completed, the shutdown hook is considered to have terminated and is not treated differently from a hook that has terminated without having thrown an uncaught exception.

De-registers a previously-registered virtual-machine shutdown hook. Hooks are compared using ==. Registration and de-registration of shutdown hooks is disallowed once the shutdown sequence has begun.

Immediately terminates the Java Virtual Machine. If the security manager denies exiting, throws SecurityException. Otherwise, termination of the Java Virtual Machine is unconditional and immediate. This method does not initiate the shutdown sequence , nor does it wait for the shutdown sequence to finish if it is already in progress. An invocation of this method never returns normally.

Executes the specified string command in a separate process.

This is a convenience method. An invocation of the form exec(command) behaves in exactly the same way as the invocation exec(command, null, null) .

Executes the specified string command in a separate process with the specified environment.

This is a convenience method. An invocation of the form exec(command, envp) behaves in exactly the same way as the invocation exec(command, envp, null) .

Executes the specified string command in a separate process with the specified environment and working directory.

This is a convenience method. An invocation of the form exec(command, envp, dir) behaves in exactly the same way as the invocation exec(cmdarray, envp, dir) , where cmdarray is an array of all the tokens in command.

More precisely, the command string is broken into tokens using a StringTokenizer created by the call new StringTokenizer(command) with no further modification of the character categories. The tokens produced by the tokenizer are then placed in the new string array cmdarray, in the same order.

Executes the specified command and arguments in a separate process.

This is a convenience method. An invocation of the form exec(cmdarray) behaves in exactly the same way as the invocation exec(cmdarray, null, null) .

Executes the specified command and arguments in a separate process with the specified environment.

This is a convenience method. An invocation of the form exec(cmdarray, envp) behaves in exactly the same way as the invocation exec(cmdarray, envp, null) .

Executes the specified command and arguments in a separate process with the specified environment and working directory.

Given an array of strings cmdarray, representing the tokens of a command line, and an array of strings envp, representing "environment" variable settings, this method creates a new process in which to execute the specified command.

This method checks that cmdarray is a valid operating system command. Which commands are valid is system-dependent, but at the very least the command must be a non-empty list of non-null strings.

If envp is null, the subprocess inherits the environment settings of the current process.

A minimal set of system dependent environment variables may be required to start a process on some operating systems. As a result, the subprocess may inherit additional environment variable settings beyond those in the specified environment. The minimal set of system dependent environment variables may override the values provided in the environment.

ProcessBuilder.start() is now the preferred way to start a process with a modified environment.

The working directory of the new subprocess is specified by dir. If dir is null, the subprocess inherits the current working directory of the current process.

If a security manager exists, its checkExec method is invoked with the first component of the array cmdarray as its argument. This may result in a SecurityException being thrown.

Starting an operating system process is highly system-dependent. Among the many things that can go wrong are:

• The operating system program file was not found.
• Access to the program file was denied.
• The working directory does not exist.

In such cases an exception will be thrown. The exact nature of the exception is system-dependent, but it will always be a subclass of IOException.

If the operating system does not support the creation of processes, an UnsupportedOperationException will be thrown.

Returns the number of processors available to the Java virtual machine.

This value may change during a particular invocation of the virtual machine. Applications that are sensitive to the number of available processors should therefore occasionally poll this property and adjust their resource usage appropriately.

Returns the amount of free memory in the Java Virtual Machine. Calling the gc method may result in increasing the value returned by freeMemory.

Returns the total amount of memory in the Java virtual machine. The value returned by this method may vary over time, depending on the host environment.

Note that the amount of memory required to hold an object of any given type may be implementation-dependent.

Returns the maximum amount of memory that the Java virtual machine will attempt to use. If there is no inherent limit then the value Long.MAX_VALUE will be returned.

Runs the garbage collector in the Java Virtual Machine.

Calling this method suggests that the Java Virtual Machine expend effort toward recycling unused objects in order to make the memory they currently occupy available for reuse by the Java Virtual Machine. When control returns from the method call, the Java Virtual Machine has made a best effort to reclaim space from all unused objects. There is no guarantee that this effort will recycle any particular number of unused objects, reclaim any particular amount of space, or complete at any particular time, if at all, before the method returns or ever. There is also no guarantee that this effort will determine the change of reachability in any particular number of objects, or that any particular number of Reference objects will be cleared and enqueued.

The name gc stands for "garbage collector". The Java Virtual Machine performs this recycling process automatically as needed, in a separate thread, even if the gc method is not invoked explicitly.

The method System.gc() is the conventional and convenient means of invoking this method.

Runs the finalization methods of any objects pending finalization. Calling this method suggests that the Java virtual machine expend effort toward running the finalize methods of objects that have been found to be discarded but whose finalize methods have not yet been run. When control returns from the method call, the virtual machine has made a best effort to complete all outstanding finalizations.

The virtual machine performs the finalization process automatically as needed, in a separate thread, if the runFinalization method is not invoked explicitly.

The method System.runFinalization() is the conventional and convenient means of invoking this method.

Loads the native library specified by the filename argument. The filename argument must be an absolute path name. (for example Runtime.getRuntime().load("/home/avh/lib/libX11.so");). If the filename argument, when stripped of any platform-specific library prefix, path, and file extension, indicates a library whose name is, for example, L, and a native library called L is statically linked with the VM, then the JNI_OnLoad_L function exported by the library is invoked rather than attempting to load a dynamic library. A filename matching the argument does not have to exist in the file system. See the JNI Specification for more details. Otherwise, the filename argument is mapped to a native library image in an implementation-dependent manner.

First, if there is a security manager, its checkLink method is called with the filename as its argument. This may result in a security exception.

This is similar to the method loadLibrary(String)^RESTRICTED, but it accepts a general file name as an argument rather than just a library name, allowing any file of native code to be loaded.

The method System.load(String)^RESTRICTED is the conventional and convenient means of invoking this method.

Loads the native library specified by the filename argument. The filename argument must be an absolute path name. (for example Runtime.getRuntime().load("/home/avh/lib/libX11.so");). If the filename argument, when stripped of any platform-specific library prefix, path, and file extension, indicates a library whose name is, for example, L, and a native library called L is statically linked with the VM, then the JNI_OnLoad_L function exported by the library is invoked rather than attempting to load a dynamic library. A filename matching the argument does not have to exist in the file system. See the JNI Specification for more details. Otherwise, the filename argument is mapped to a native library image in an implementation-dependent manner.

First, if there is a security manager, its checkLink method is called with the filename as its argument. This may result in a security exception.

This is similar to the method loadLibrary(String), but it accepts a general file name as an argument rather than just a library name, allowing any file of native code to be loaded.

The method System.load(String) is the conventional and convenient means of invoking this method.

Loads the native library specified by the filename argument. The filename argument must be an absolute path name. (for example Runtime.getRuntime().load("/home/avh/lib/libX11.so");). If the filename argument, when stripped of any platform-specific library prefix, path, and file extension, indicates a library whose name is, for example, L, and a native library called L is statically linked with the VM, then the JNI_OnLoad_L function exported by the library is invoked rather than attempting to load a dynamic library. A filename matching the argument does not have to exist in the file system. See the JNI Specification for more details. Otherwise, the filename argument is mapped to a native library image in an implementation-dependent manner.

First, if there is a security manager, its checkLink method is called with the filename as its argument. This may result in a security exception.

This is similar to the method loadLibrary(String)^RESTRICTED, but it accepts a general file name as an argument rather than just a library name, allowing any file of native code to be loaded.

The method System.load(String)^RESTRICTED is the conventional and convenient means of invoking this method.

Loads the native library specified by the libname argument. The libname argument must not contain any platform specific prefix, file extension or path. If a native library called libname is statically linked with the VM, then the JNI_OnLoad_libname function exported by the library is invoked. See the JNI Specification for more details. Otherwise, the libname argument is loaded from a system library location and mapped to a native library image in an implementation-dependent manner.

First, if there is a security manager, its checkLink method is called with the libname as its argument. This may result in a security exception.

The method System.loadLibrary(String)^RESTRICTED is the conventional and convenient means of invoking this method. If native methods are to be used in the implementation of a class, a standard strategy is to put the native code in a library file (call it LibFile) and then to put a static initializer:

 static { System.loadLibrary("LibFile"); }
 

within the class declaration. When the class is loaded and initialized, the necessary native code implementation for the native methods will then be loaded as well.

If this method is called more than once with the same library name, the second and subsequent calls are ignored.

Loads the native library specified by the libname argument. The libname argument must not contain any platform specific prefix, file extension or path. If a native library called libname is statically linked with the VM, then the JNI_OnLoad_libname function exported by the library is invoked. See the JNI Specification for more details. Otherwise, the libname argument is loaded from a system library location and mapped to a native library image in an implementation-dependent manner.

First, if there is a security manager, its checkLink method is called with the libname as its argument. This may result in a security exception.

The method System.loadLibrary(String) is the conventional and convenient means of invoking this method. If native methods are to be used in the implementation of a class, a standard strategy is to put the native code in a library file (call it LibFile) and then to put a static initializer:

 static { System.loadLibrary("LibFile"); }
 

within the class declaration. When the class is loaded and initialized, the necessary native code implementation for the native methods will then be loaded as well.

If this method is called more than once with the same library name, the second and subsequent calls are ignored.

Loads the native library specified by the libname argument. The libname argument must not contain any platform specific prefix, file extension or path. If a native library called libname is statically linked with the VM, then the JNI_OnLoad_libname function exported by the library is invoked. See the JNI Specification for more details. Otherwise, the libname argument is loaded from a system library location and mapped to a native library image in an implementation-dependent manner.

First, if there is a security manager, its checkLink method is called with the libname as its argument. This may result in a security exception.

The method System.loadLibrary(String)^RESTRICTED is the conventional and convenient means of invoking this method. If native methods are to be used in the implementation of a class, a standard strategy is to put the native code in a library file (call it LibFile) and then to put a static initializer:

 static { System.loadLibrary("LibFile"); }
 

within the class declaration. When the class is loaded and initialized, the necessary native code implementation for the native methods will then be loaded as well.

If this method is called more than once with the same library name, the second and subsequent calls are ignored.

Returns the version of the Java Runtime Environment as a Runtime.Version.